Tube clamp for a tube bending tool



March 18, 1969 R. P. CRIHFIELD ETAL 3,433,042

TUBE CLAMP FOR A TUBE BENDING TOOL Filed March 10, 1967 RIHFIELD 8 DODGE I NVEN TORS RICHARD P. C HARRY G.

ATTORNEYS United States Patent Claims ABSTRACT OF THE DISCLOSURE This application relates to a tube clamp which is utilized on a tube bending tool. The tube clamp has a swinging arm which has one end pivotally mounted on a tube clamp bar. The other end of the arm curves to form an arced section and a slot is cut therein. A handle passes through the slot from the outside and connects with an arcuate locking jaw at the inner face of the arced section of the arm. The arcuate locking jaw is rotatable by means of the handle to grasp and release a tube in the tube bending tool.

Background of the invention- There are several problems in bending a tube with a tube bending tool. The tube must be held securely by a tube clamp arm to eliminate slipping and prevent nicks or indentations. Moreover, if the tube clamp does not give adequate support, the tube may experience a necking down or an eccentricity at the cross section of its bend. As a matter of convenience and economics the tube clamp should also facilitate the fastest possible positioning of the tubes in the tube bender.

Several types of tube clamps have been proposed. The typical tube clamp, as shown in Patent No. 3,236,082 to Beck et 211., has a narrow arm which is pivotably mounted at one end and has a leg extending from the other end. The leg is usually perpendicular to the arm of the tube bending tool. This type of tube clamp gives only limited support to the tube during the bending operation since it provides minimal contact with the periphery of the tube. That is, the tube clamp does not surround and uniformly support the tube during the severe stresses of bending.

Clamping arms, as illustrated in Patent No. 1,901,762 to Meyer, have also been proposed which in addition to a pivoted arm and a downwardly extending leg have a recess in the leg to conform to the shape of the tube which it supports. In order to bring the recess into contact with the periphery of the tube it is necessary not only to swing the clamping arm into position, but also to move it laterally away from the tube so that the leg may clear the tube. Once the arm is resting on the tube, the clamp must again be moved laterally to bring the recessed portion of the leg into position against the tube. This double motion necessarily requires a more complex apparatus than the simple swinging tube clamp arm.

This invention contemplates a clamping arm that provides excellent support around the periphery of the tube. The arm minimizes nicking, necking down and eccentricity resulting from the tube bending procedure but holds the tube securely to prevent slipping. Moreover, the clamping arm is a simple mechanism which is easily placed on the tube and removed with one continuous motion.

Summary of the invention The clamping arm is pivoted at one end and extends outwardly from the pivot point until it curves and extends to form a leg at an angle to the axis of the arm. A longitudinal slot is formed in the curved portion of the arm and extending therethrough is a handle connected to an arcuately shaped locking jaw. The locking jaw moves along the inner surface of the arced section of the arm when rotated by the handle. The handle may thus be used to swing the arm into position and clamp the jaw over the tube thus firmly supporting it. Moreover, the tube may be released with one simple continuous motion which unlocks the tube and removes the arm.

FIG. 1 is a top plan view of the tube bending apparatus of this invention.

FIG. 2 is a side view of the tube clamp of this invention and is taken through section 22 of FIG. 1.

FIG. 3 is a side view of the tube clamp in an open position.

FIG. 4 is a top view of the tube clamp and is taken along section 44 of FIG. 2.

A tube bender of the general type shown in U.S. Patent No. 3,236,082 is illustrated in FIG. 1 and includes a case 10 with a cover plate 11. Extending from one side of the cover plate 11 is a crank arm 13 which may be rotated by means of a hand grasp roller 14 at the outer end thereof. Through appropriate gearing and a drive shaft (not shown), the crank arm 13 turns a forming roller 15.

The forming roller 15 is secured by a screw 17 whose body passes through an apertured disc 16. The head of the screw 17 is larger than the aperture, and when in place holds the disc 16 against the forming roller 15. A degree scale 20 is marked on the cover plate 11 in order to allow the operator to predetermine the degree of bend of the tube 18.

In close proximity to the forming roller 15 is a guide 21 which holds the tube 18 against the forming roller 15. The guide 21 has a U frame member 22 supporting rotatably mounted idler tube rollers 23 and 24. It is anticipated, however, that the guide 21 may have various configurations including a straight tangential member having a recess therein to conform to the shape of the tube.

A tube clamp bar 26 has a reduced diameter section 27 which is threadedly engaged with the forming roller 15. The tube clamp bar 26 acts in conjunction with a pointer 28 to govern the degree of bending of a tube 18. The pointer 28 is manually set and locked by means of an adjustment knob 29 to a setting on the degree scale 20. As the forming roller 15 is turned, the clamp bar 26 rotates until it is stopped by the pointer 28. Since the tube clamp bar 26 secures one end of the tube 18, any preselected degree of bend can be formed by setting the pointer 28.

A tube stop 30 is attached to the tube clamp bar 26. A knob 31 adjusts a locking mechanism (not shown) on the tube stop 30 so that it may be located at any point along the length of the bar 26.

In order to secure the end of the tube 18, a tube abutment 33 and a centering tip 34 extend transversely from the tube stop 30 into the tube 18. One end of the tube 18 is placed over the centering tip 34 against the abutment 33 whereupon the knob 31 locks the tube stop 30 in position on the tube clamp bar 26.

Pivotally mounted on the tube clamp bar 26 is a tube clamp 37. As noted in FIGS. 2, 3 and 4, the tube clamp 37 has one end pivotally mounted about the tube clamp bar 26. The tube clamp 37 extends radially from the bar 26 to form an arm 38 which curves at 39 and subsequently forms a leg which is at an angle from the arm 38. The curved portion 39 of the tube clamp 37 has a slot 40 along its length which permits a handle 44 to be inserted therethrough. In practice the slot 40 extends through approximately on the arced portion 39 whereby the handle 44 may rotate through the same number of degrees. The handle 44 has a collar 45 at one end in abutting relationship to the outer surface of arced portion 39. An arcuate locking jaw 46 is attached near the center of its outer periphery to the handle 44 so that the locking jaw may slide along the inner face 47 of the arced portion 39. A cross section of the locking jaw 46 forms an arc of a circle of approximately 180 to conform and give maximum support to the outer wall of the tube 18.

In addition to the support by the locking jaw 46 to about 180 of the tubes circumference, approximately one-half of the remainder of the tubes circumference is held by the groove or recess of the bending roller 15. Thus, the tube 18 is virtually supported around its entire circumference. This total support is possible because of the rotatable locking jaw 46. If the locking jaw 46 were permanently secured in its down or locking position (FIG. 2) approximately 90 of the locking jaw 46 would extend into the path through which the arm 38 must pass to come into contact with the tube 18.

Conversely, if the locking jaw 46 were always in its unlocked position, then it would only support 90 of the circumference of the tube 18.

In operation a tube 18 is put in position in the peripheral groove in the forming roller and its end is placed over the centering tip 34 on the tube stop 30. The clamp 37 is then grasped by the handle 44 and rotated from its position as seen in FIG. 3 to a position where the arm 38 is generally parallel with the cover plate 11. Once it is in this position, a continuation of the motion with the handle 44 rotates the arced locking jaw 90 around the tube 18, thus supporting it about 180 of its circumference (FIGS. 2 and 4).

To release the tube 18, the handle 44 is rotated clockwise as seen in FIGS. 2 and 3, and the clamping arm 38 is raised from engagement with the tube 18.

During bending of a tube there is a natural tendency for the bent section to become eccentric, that is, to narrow or neck down. This necking down is caused by the fact that the outer section of the bend must travel or stretch further than the inner section. The natural resistance to stretching of the metal on the outer section causes it to converge on the inner section. To preserve the circular cross-section of the tube, the portion to be bent must be adequately supported. In the instant invention the locking jaw 46 supports one-half of the circumference and the forming roller 15 supports the other half, thus frustrating any tendency for the tube to stem down or become eccentric during bending.

During the high stresses of bending a tube, narrow clamping devices have a tendency to nick or dent the tube which they hold. The present locking jaw 36 has been given a relatively large surface area to prevent precisely this phenomena as well as to prevent slipping.

For ease of description, the principles of the invention have been set forth in connection with but a single illustrated embodiment. It is not my intention that the illustrated embodiment nor the terminology employed in describing it .be limiting inasmuch as variations in these may be made without departing from the spirit of the invention. Rather I desire to be restricted only by the scope of the appended claims.

I claim:

1. In a tube bending tool having a forming roller, means for turning said forming roller, a tube clamp bar engaged with said forming roller and a tube clamp; said tube against said forming roller and a tube clamp; the improvement of said tube clamp comprising:

an arm pivotally secured at one end thereof to said tube clamp bar;

said arm extending radially from said tube clamp bar and arcing to form a leg at an angle with said arm; and

rotatable means on said arm for grasping a tube; said rotatable means coacting with said arm to support said tube at least both above and below its centerline.

2. The tube bending tool of claim 1 wherein said rotatable means includes a locking jaw which is slidable along and in an abutting relationship to the inner surface of the arced section of said arm.

3. The tube bending tool of claim 2 which further includes a slot located along the arced section of said arm and a handle passing therethrough which engages said locking jaw for movement relative to said arm.

4. The tube bending tool of claim 3 wherein said arcuate-shaped jaw is approximately semi-circular.

5. The tube bending tool of claim 4 wherein said semicircular jaw is rotatable approximately by said handle so that the arm and semi-circular jaw may be placed over a tube and then locked in place by rotating the semi- I circular jaw with the handle.

References Cited UNITED STATES PATENTS 643,760 2/1900 Brinkman 72-154 1,901,762 3/1933 Meyer 72-154 3,004,583 10/1961 Zuccala et al. 72-157 CHARLES W. LANHAM, Primary Examiner.

RONALD D. GREFE, Assistant Examiner.

U.S. Cl. X.R. 

